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Outline
• Canadian history of soil quality/health concerns
• US history of soil quality/health concerns
• Soil quality vs soil health definitions
• Current understanding of soil health
• Human Microbiome Project – parallels with soil health
2
Canadian History
• 1980s: Decade of awareness of soil degradation:-
– Erosion (wind and water), salinization, OM loss, urban encroachment.
– 1984: Senate report “Soil at risk: Canada’s eroding future”.
– Other reports: Federal and provincial departments of agriculture,
universities, Agric. Institute of Canada (AIC).3
Canadian History
• 1990s: Decade of healing –
– finding ways to measure and improve soil quality.
• AAFC: Centre for Land & Biological Resources (Ottawa) formed.
– The Soil Quality Evaluation Program (SQEP) formed.
– Goal: Develop a national capability to assess soil and associated
environmental quality, and the effects of land use and management
practices.
• 1995: Book “The Health of our Soils: Toward sustainable
agriculture in Canada”.
4
Canadian History
• 1995 Book: “The health of our soils – Toward sustainable
agriculture in Canada” :-
– Soil health, or quality, is the soil’s fitness to support crop growth without
resulting in soil degradation or otherwise harming the environment”.
• “The terms soil health and soil quality can be used
interchangeably”.
• Emphasized crop production, but had concerns about the
environment.
• No chapter on soil microbiology (although listed in the first
chapter as an indicator of soil quality). 5
Soil Fertility
• Soil fertility: The natural, sustainable ability of a soil to produce
plants (Anonymous, 2016: “The Basics of Soil Fertility: Shaping
our Relationship to the Soil” – Organic Research Centre, UK).
– Nutrient content: Fertility indicator.
– Crop yield: Fertility measurement.
• The capacity of the soil to supply nutrients to a crop (Chatterjee,
2017: “Soil Fertility Management in Agroecosystems” – ASA,
CSSA, SSSA).
• Soil fertility – one aspect of soil quality/health.
6
USA• Similar discussions in US, after the National Academy of
Sciences published the book: “Soil and Water Quality: An
Agenda for Agriculture” (National Research Council, 1993).
• 1996 Book: “Methods for Assessing Soil Quality – SSSA Special
Pub. # 49” :-
– Soil quality simple definition: The capacity of a soil to function.
– how well the soil does what we want it to do.
• Recognized multiple functions of soil, including ecological
functions.
• Soil functions: water flow and retention, solute transport and retention,
physical stability and support; retention and cycling of nutrients; buffering
and filtering of potentially toxic materials; and maintenance of biodiversity
and habitat. 7
USA
• Ecological definition of soil quality (recognizes multiple soil
functions (Doran & Parkin, 1994: “Defining and Assessing Soil
Quality” SSSA Special Pub. #35):-
– The capacity of soil to function, within land use and ecosystem
boundaries, to sustain biological (plant and animal) productivity, maintain
(or enhance) environmental (water and air) quality, and promote plant,
animal and human health”.
8
Soil Quality vs Soil Health
• “The terms soil quality and soil health are often used
interchangeably” (“Methods for Assessing Soil Quality), but noted
preferences:-
– Producers prefer “soil health”, which portrays soil as a living, dynamic
organism that functions holistically rather than an inanimate mixture of
sand, silt and clay.
• Characterized on the basis of descriptive and qualitative properties.
– Soil scientists prefer “soil quality”, which describes quantifiable physical,
chemical and biological characteristics.
• To scientists, soil “health” requires value judgements that cannot be
quantified.. 9
Soil Quality vs Soil Health
• US conference recommendation: Soil health definition should:-
– reflect the soil as a living system
– address all essential functions soil in the landscape
– compare the condition of a given soil against its own unique potential
within climatic, landscape and vegetation patterns
– enable assessment of trends.
• Same concepts as soil quality, except “living” and “trends”.
10
Soil Quality vs Soil Health
• Soil quality: the capacity of a soil to function, within land use and
ecosystem boundaries, to sustain biological productivity,
maintain environmental (air and water) quality, and promote
plant, animal and human health”.
• Soil health: the continued capacity of soil to function as a vital
living system, within ecosystem and land-use boundaries, to
sustain biological productivity, maintain the quality of air and
water environments, and promote plant, animal, and human
health.” (Doran et al. 1996: Adv. Agron. 56).
– Soil health: broader aspects and multiple soil functions, and puts
particular emphasis on soil as an integrated, dynamic, living system.11
Current Understanding of Soil Health
• Emphasis on soil as a living system - shifting focus to soil
biology.
• Soil biology and its importance to soil health - less attention in
the past because:-
– Difficult to measure. New molecular methods have changed that.
– Significance not fully appreciated. We now know that they affect :-
• soil structure, erosion, and water availability, decomposition, nutrient
cycling, breakdown of toxins, and suppression of pests, and are
responsible for a large proportion of the world’s genetic diversity.
• Influence of the Human Microbiome Project. 12
Soil (Rhizosphere)
15
Soil – more biodiversity than aboveground communities .
The plant root = “inside-out” gut .
Emphasis on Soil Biology: Gut vs Soil Microbiome
Issue Gut Soil
Normal state Diverse microbiome Diverse microbiome
Changes to normal state The food we eat - processed
vs fresh food, antibiotics
Crop/soil management –
tillage, fertilizers vs manures,
pesticides, antibiotics
Results of “abnormal/impaired”
microbiome
Poor health, e.g., obesity,
diabetes
Soil degradation (OM loss, soil
structure), environmental
pollution
Corrective measures Probiotics (targeted microbes)
and prebiotics (microbial food)
Add/boot soil microbial
consortia (probiotics) and
organic C amendments
(prebiotics)16
Lessons from the Human Microbiome Project
17
• Nutrient management: Should combine biology with
chemistry (integrated nutrient management), not
chemistry alone.
• All major agro-chemical companies now - doing
research on biological products:-
– http://www.monsanto.com/products/pages/microbials.aspx
– https://agriculture.basf.com/en.html
– http://www.dupont.com/corporate-functions/our-
approach/strategic-priorities/bio-based-industrials.html
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